ME6 - Transformers Flashcards Preview

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Flashcards in ME6 - Transformers Deck (17):
1

What do transformers do?

Change the size of the voltage of an alternating current

2

What do all transformers have?

Two coils, the primary and the secondary, joined with an iron core

3

What happens when you apply an alternating voltage across a primary coil?

The magnetically soft (iron) core magnetises and demagnetises quickly. This induces an alternating voltage in the secondary coil

4

The ratio between the primary and secondary voltages is the same as what ratio?

The ratio between the number of turns on the primary and secondary coils

5

What are step up transformers?

They step the voltage up - they have more turns on the secondary coil than the primary coil

6

What are step down transformers?

They step the voltage down - they have more turns on the primary coil than the secondary

7

What do you need to know to calculate the output voltage from a transformer?

The input voltage and the number of turns on each coil

8

What is the word equation for transformers?

Input (primary) voltage /Output (secondary) voltage = Number of turns on primary/ number of turns on secondary

9

What are the other two equations you can use for transformers?

Vp/Vs = Np/Ns or both equations flipped around

10

If transformers are nearly 100% what does that mean?

Power in = power out

11

What is the general formula for power supplied?

Power = voltage x current or P= V x I

12

How can you rewrite input power = output power for transformers?

VpIp = VsIs

Vp = Primary voltage
Ip = Primary current
Vs = Secondary voltage
Is = Secondary current

13

What do transformers make more efficient?

Transmitting mains electricity

14

What are the main purposes of using step up and step down transformers?

Used when transmitting electricity across the country

15

Why is the voltage not transmitted efficiently in power stations?

It is too low - the lower the voltage the higher the current for a given amount of power, causing the wire to heat up

16

What are step up transformers used for in the power station?

To boost the voltage before it is transmitted

17

What are step down transformers used for in power stations?

Used at the end of the journey to reduce the voltage so its more useful and safer to use